SCREENINGS. 
65 
From the foregoing observations it appears that a great deal of 
impurity is shipped with the Wheat; also that these refuse accompani¬ 
ments are quite unnecessary to the extent to which they come; also 
that their presence to a great extent may be prevented by joint action 
of importers, excepting, of course, where a stated amount of adultera¬ 
tion is permitted; and further, that these refuse-matters are not 
desired by millers, as their presence entails necessity for expensive 
machinery which would not otherwise be wanted. 
Therefore, as it appears that the absence of refuse in the corn- 
cargoes would not injuriously affect the importers or millers, but, on 
the contrary, that clean cargoes would be preferred, it is allowable to 
draw attention, agriculturally, to the great risks that are run by 
purchase of what is (or in all probability may be) infested refuse, and 
thus in various ways allowing noxious insects, eelworms, fungi, or 
weeds to gain a footing. 
The great hope that we may not suffer in field produce from this 
cause lies in the notable fact that imported field-pests (at least as far 
as America is concerned) have not taken hold here to any degree; com¬ 
pared, that is, to what our pests do in America ; and therefore we may 
hope to continue to be tolerably free. Still, Hessian Fly, though 
probably derived from Europe, has made good a footing, and there are 
two or three other attacks which, under present circumstances, it would 
be well to be on the watch for. 
One is the “ Joint-worm ” of North America, the Isosoma horclei, 
Isosoma hordei, Harris. 
Female and antenna ; male and antenna (all much magnified). Nat. length of 
fly about one-tenth of an inch or rather more. Galls on straw caused by Joint- 
worm. 
Harris (figured above), together with some bits of straw showing the 
galls by which this attack may be recognised. This joint-worm lays 
its eggs in summer in the stalk of the growing plant of Wheat, Barley, 
